In a very deep hot water well temperatures may be of the order of 400.degree.-500.degree. F. with a corresponding vapor pressure of several hundred pounds per square inch. When pumping such hot water to the surface, the pressure must be kept high enough to prevent boiling and flashing into steam, both at the pump inlet and at the surface. Accordingly, it is necessary to submerge any pump for such hot water very deep therein, i.e. to depths of as much as 800 feet, in order to maintain vapor pressure at the pump inlet above boiling at the existing water temperature.
The location and environment of such pumps give rise to many problems, most of which render it impractical to drive the pump by a shaft extending from the well mouth. For this reason pumps have been devised and constructed in the form of self-contained units which include a turbine for driving a centrifugal pump. Even so, many problems still exist in supplying motive fluid for the turbine from the surface to depths of the order of 1000 feet or more; minimizing wear on the turbine and pump bearings, both during operation and start-up, at the high temperatures and pressures involved; minimizing leakages in the unit to maximize its efficiency; accomplishing low cost design which will also minimize potential maintenance; effectively sealing the unit to the well casing; avoiding undue, tensile and/or compressive stresses in the motive fluid supply conduit; etc.
Attempts have been made to solve some of the foregoing problems, as exemplified by the disclosures of the following patents: Bigelow, U.S. Pat. No. 1,894,393; Harney, U.S. Pat. No. 3,171,629; and Nichols, U.S. Pat. No. 3,961,899. None of the prior attempts, however, have been completely successful.